Web Coverage Service (WCS)
Purpose
The OGC Web Coverage Service (WCS) standards suite defines services on coverages. The standards are available from http://www.opengeospatial.org/standards/wcs.
A coverage is defined as a "space-time varying phenomenon", such as 1D sensor time series, 2D remote sensing imagery, 3D x/y/t satellite image time series and x/y/z geophysical data, as well as 4D x/y/z/t atmospheric and ocean data. A normative abstract definition of coverages is given in OGC Abstract Topic 6 (which is identical to ISO 19123), a concrete definition is provided with the OGC GML Application Schema for Coverages, available from http://www.opengeospatial.org/standards/gml.
On this OGC Networks page you find details about specification documents and files, information about
supplementary material explaining use of WCS, and a list of WCS implementations & services known to us. More about the WCS Standards Working Group (WCS.SWG) we provide an overview on the Standard Working Group's agenda and some details on OGC Working Groups collaborating on coverages and WCS.
Contact points: Peter Baumann (chair) and Stephan Meissl (co-chair).
News
December 2011: a proposal for OGC Name Type Specification for Coordinate Reference Systems (CRSs) has been presented, together with an open-source registry implementation. During the next weeks this resolver will be set up as a prototype service by OGC.
December 2011: Corrigenda have been adopted by the WCS Standards Working Group:
- to enhance the OGC Coverage Model with flexible encoding support: pure GML, any special encoding format (identified by its MIME type), and a mixed representation containing a GML metadata header followed by the binary encoding, transmitted as Multipart/Related document. Following final edits it will be rolled out for voting.
- to enhance WCS Core with parameters to request specific format encodings and to use Coordinate Reference Systems (CRSs) different from the coverage's native CRS. Following final edits it will be rolled out for voting.
August 2010: the WCS 2.0 suite has been adopted as official OGC standards. Following careful modularization, specifications have been split into the coverage data structure definition, available with GML, and the service definition, available with WCS.
WCS 2.0 has several significant advantages over previous versions: it relies on the GML coverage model, leading to increased interoperability across OGC standards; main features are:
- extends beyond pure raster grids to support all coverage types which GML 3.2.1 knows, e.g., curvilinear grids, irregular grids, point clouds, surface coverages; general meshes;
- crisp and modular, consisting of a small mandatory core and a structured universe of optional extensions;
- harmonized with OGC OWS-Common, GML, SWE, WMS, WCPS, and WPS
- has a clear, formally specified syntax (XML Schema) and semantics (Schematron) easing understanding and implementation;
- testable: for the first time, pixel contents is subject to conformance testing.
Attention is drawn to the fact that the coverage examples provided with the XML Schema are inconsistent with SWE Common 2.0. This is due to the fact that SWE Common 2.0 has undergone some last minute changes before its adoption and after WCS 2.0 adoption. The WCS.SWG will adjust the examples in due course.
Background
"The Web Coverage Service (WCS) supports electronic retrieval of geospatial data as "coverages" – that is, digital geospatial information representing space-varying phenomena.
A WCS provides access to potentially detailed and rich sets of geospatial information, in forms that are useful for client-side rendering, multi-valued coverages, and input into scientific models and other clients. The WCS may be compared to the OGC Web Map Service (WMS) and the Web Feature Service (WFS); like them it allows clients to choose portions of a server's information holdings based on spatial constraints and other criteria.
Unlike the WMS [OGC 06-042], which portrays spatial data to return static maps (rendered as pictures by the server), the Web Coverage Service provide s available data together with their detailed descriptions; defines a rich syntax for requests against these data; and returns data with its original semantics (instead of pictures) which may be interpreted, extrapolated, etc. – and not just portrayed.
Unlike WFS [OGC 04-094], which returns discrete geospatial features, the Web Coverage Service returns coverages representing space-varying phenomena that relate a spatio-temporal domain to a (possibly multidimensional) range of properties."
-- WCS 1.1.2 [OGC 07-067r3]
Disclaimer
This website contains statements by both members of the WCS Standards Working Group (WCS.SWG) and other groups and individuals. Any opinions expressed by members of the WCS.SWG are reflecting their individual position. Under no circumstance any information provided here can be interpreted as normative or as a statement on directions any OGC specification (in particular: the WCS suite) is taking, is likely to be taken, or is intended to be taken. Further, no information provided here can be interpreted as endorsed by OGC. Finally, links from this page to web space outside the domain of the OGC do not constitute any endorsement or support for the contents of the web page / site referenced; generally speaking, OGC is not responsible in any way for the contents of such sites.